Cleaned up and simplified the config/env.sh and util/build.sh

 - We should limit the number of new environment variables. They
 increase complexity which should be mostly absorbed by using containers.
 - Any new environment variables should be set via the ci yml file
 or defined the UI. https://docs.gitlab.com/ee/ci/variables/README.html#custom-environment-variables
 - Removed dummy scripts
 - Removed dvmp dummy jobs.
 - Fixed dvmp output data. Note the out artifacts should go in
 `results/dvmp` if they are in the `dvmp` directory. This will just make
 things easier later on for collecting and summarizing results.
 - updated  dvmp/scripts/run_generator_instance.sh
 - Added dvmp.sh to run geant4/reconstruction. Note `dvmp/dvmp.sh` could be named something more specific, like `dvmp/dvmp_barrel_decays.sh` depending on the input, analysis, etc...